I have a question about the secondary side of the carb. It is a standard marine Holley 600 with electric choke. The motor is running and idling good, but the back barrels don't seem to be opening up. I have taken the rpm's to 4000 on the trailer but still not opening. Not sure what is going on . Any help appreciated!!

They won't open up unless the engine is under load. You won't be able to get the vacuum low enough without doing some damage to your engine. If you are suspecting that they aren't opening, you will need to do an on the water test with the engine cover open or off to see.